Lamp manufacture



Patented July. 4, 1933 um'ran STATES PATENT OFFICE MARK N. IREDENBURGH, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTING- HOUSE LAMP COMPANY, A OOBPOR IA'IION OF PENNSYLVANIA LAMP MANUFACTURE No Drawing.

method of incorporating the same within the device.

One of the object's'of the present invention is to provide a heat resistant phosphorus getter admixture.

Another object of the present invention is to provide a method of incorporating the same in a coil type filament.

.Another object of the present invention is to improve the exhaust of evacuated devices.

.Other objects and advantages will be apparent'as the invention is more fully disclosed.

In cop'ending application by 'D. S. Gustin filed May 11, 1928 entitled Process for getterin coilslis'disclosed a method of applying a ry getter composition to coil type incandescent lamp filaments. Briefly described the process comprises substantially in finely comminuting the getter composition, incorporating therein the coiled filaments, and then tumbling the coils about in the finely comminuted getter material, thereby mechanically compacting the getter within the coil turns and interstices of the coiled filament.

. The getter composition usually employed is comprised of an admixture of phosphorus and cryolite (or sodium ferric fluoride) the phosphorus being present in the admixture in amounts varying from l to parts.

It is customary in the manufacture ofv lamps and other evacuated devices, to subject the enclosing envelope to a=relatively high temperature during the exhaust opera tion in order to effect substantial degasificaf tion ofthe same. .With incandescent lamps this baking out temperature is dependent upon-the specific glass composition and is also in part dependent upon the relative vola-ltility and'activity of the getter composition employed.

In the specific getter composition set forth Application filed August '21, 1930. Serial No. 478,951.

are employed appreciable oxidation of the I phosphorus is obtained, the amount thereof lncreaslng w1th increased temperatuies, time of exposure thereto and other factors. This progressrve loss in getter material is reflected 1n var1at1ons 1n the degree of evacuation obtamed by reason of the subsequent residual gas cleanup upon the flashing of the getter .from the filament.- 4

I have found that this progressive oxidat1on of the phosphorus during the baking out process maybe substantially prevented by comprising the getter material of relatively coarse phosphorus particles and very finely commmuted cryolite (or sodium ferric fluor- 1de),'the finely comminuted cryolite serving to coat the phosphorus with a relatively adherent heat insulating coating.

c I have also found that by thus comprising the getter composition of a relatively coarse and a relatlvely fine constituent the method of applying the same to the coil type filament must be improved in order to obtain the advantagesof the dry getter method of Gustin above identified.

The specific improvement of the present invention comprises'the addition of a suitable binder material to the getter composition in order to facilitate the mechanical c'ompaction of the same within the interstices of the filament coils. The specific binder to-be employed must obviously be inert with respect to' the phosphorus, thermally vaporizable at relatively low temperatures without decomposition into deleterious products and readily evacuated from the device when in the vapor state. Specifically I have found that organic bin er materials most suitable forthe purposes of the'present' invention.

As a specific embodiment of the practice of the present invention I first prepare the comdpounds, such as diethyl phthalate are the cryolite (or sodium ferric fluoride) ina he 1y comminuted state by ball milling the same for a' prolonged interval of time, approximately 120 hours. In this fine state of .sub-' division the cryolite readily passes the finest mesh, such as silk bolting cloth.

An admixture of approximately 200 grams of this material and approximately 30 grams of regular stock red phosphorus ingranulated form," such as is commonly purchased upon the market, and '230 cubic centimeters of alcohol is ball milled for 30 minutes. The time interval of'milling roughly controls the particle size of the phosphorus. The milled admixture is placed on a glass tray and the alcohol evaporated at 110 C. and the dried admixture gently brushed through a 200 5 mesh screen and bottled. The admixture is filament. The method of application of this admixnow ready for application to the coil type tents rotated so that the binder wetted zinc particles pick up the dry powder and cause it to adhere to the surfaces thereof by the adsorption of the diethyl phthalate.

The finished getter material will substantially comprise a quantity of round pellets made up of a core of zinc surrounded by a quantity of getter mixture.

These pellets are placed in a tube or other chamber together with the coiled filaments to be gettered and the tube and contents vigorously agitated as in the Gustin process above identified. "This forces the getter mixture into the core of the coil. The diethyl phthalate present acts as abinder and causes the getter mixture to pack so that future handling of the coils will not easily displace the getter.

During the preheating and baking out bf lamp the diethyl phthalate is vaporized completely away from the .mixture. The re- 'maining getter material comprising phos- \phorus in relatively coarse condition, super-- ficially coated with inert non-inflammable cryolite (or sodium ferric fluoride) withstands a higher baking temperature than the finely divided phosphorus getter composition heretofore employed. 1.

Thisisab'elieved due tothe better heat insulation afi'orded thephosphorus content of "the getter'by the inert component surrounding the same whereby the time factor necessary to reach the kindling temperature of the phosphorus is materially increased.

3 Having broadly and specifically disclosed the present invention it is apparent that there may be many modifications made of the specific embodiment herein disclosed without departing essentially from the nature and scope of the invention as may be set forth in the accompanying claim s:

vices comprising finely comminuted cryolite and relatively coarse phosphorus.

3. A getter composition for incandescent electric lamps comprising finely comminuted inert material, relative coarse phosphorus and an organic binder.

4. A getter composition for incandescent electric lamps'comprising finely'comminuted cryolite, relatively coarse phosphorus and a proportion. of diethyl phthalate.

5. The method of gettering 'coil type incandescent lamp filaments comprising forming an admixture of finely comminuted inert material and relatively coarse phosphorus addingthereto a'proportion of a vaporizable binder material, mechanically compacting the admixture within the interstices of said filament and evaporating the binder.

6. The method of gettering coil type incandescent lamp filaments comprising intimately admixing finely comminuted cryolite and relatively coarse phos horus, adding thereto .a proportion of diet yl phthalate, mechanically compacting the admixture within the interstices of said filament and evaporating the binder.

7. As an article of manufacture a coil type incandescent lamp filament vsaid filament having a compact core vof'getter material comprising finely comminuted inert material and relatively coarse phosphorus.

8. As an article of manufacture, a coil type incandescent lamp filament, said filament having a compact. coreof getter material comprising finely comminuted cryolite, and relatively coarse phosphorus.

9. As an article of manufacture, a coil type incandescent lamp filament, said filament having a core of getter material mechanically compacted therein, said core comprising relatively coarse phosphorus, relatively finely comminuted cryolite and a proportion of diethyl phthalate binder.

10. The method of introducing a pro ortion of liquid binder in finely subdivided material which comprises applying" said binder fluid to the surface of substantially spherical non-absorbent material to form a surface film thereon, adding the finely divided material thereto, and tumbling the admixture to obtain uniform adsorption of the binder fluid in the finely divided material.

In testimony whereof, I have hereunto subigriged my name this -18 th'day of August 3 MARK N. 

